The objective of this research is to determine the factors which regulate total CoA content of heart and liver, the rate of synthesis from its vitamin precursor, pantothenate, the rate of CoA degradation, and the storage of pantothenate in these tissues. The influence of metabolic and hormonal state on CoA content of livers and hearts has been established by comparing fasted to refed rats and alloxan-diabetic to normal rats. Studies on the mechanism involved will try to reproduce these changes in primary cultures of rat hepatocytes and in perfused working heart systems by addition of hormones and metabolites ascribed to the metabolic states used for the in vivo studies, or by addition of compounds which would influence the postulated feedback inhibitions. In these experiments the level, specific activity, and subcellular location of precursors, intermediates, total CoA, CoASH, and synthetic enzymes will be measured to establish the regulated steps and suggest possible effectors. To ascertain the means by which cytosolic and mitochondrial CoA contents are regulated the permeability of the mitochondrial membrane to CoA and/or precursors will be measured. The influence of CoA changes on the rates of various tissue-specific metabolic pathways will also be tested in hepatocytes in primary culture, perfused hearts, and in heart and liver mitochondria to establish the relationship of total CoA content to roles of these tissues.